Patients with cardiac vascular diseases, such as hypertension, or adult diseases, hard to cure, such as diabetes and renal failure, are recommended to limit salt or to take a small amount of salt. As salt which may be given to a patient with hypertension, there is now only salt whose sodium chloride (NaCl) content is reduced by adding potassium chloride (KCl). Even a functional salts, there are only garlic salt and green tea salt whose clinical results have not yet been found.
Hypertension is mainly described by a physiochemical mechanism caused by renin-angiotensin, and substances capable of inhibiting the activity of angiotensin converting enzyme (ACE) are currently of high concern for direct inhibition of hypertension. In addition to producing dipeptide, ACE is presumed to show an enzyme reaction mechanism similar to pancreatic carboxypeptidase A. On the basis of this presumption, chemically synthesized ACE inhibitor, such as captopril and enarapril, are used as antihypertensive agents. However, since such chemical products have many problems, such as safety, side effects, and the like, the searching of peptide-based ACE inhibitory substance from various natural substances is being continued.
Steady intake of food containing the ACE inhibitory substance will help the prevention or alleviation of hypertension. Chitosan is one of the biopolymer substances, prepared by deacetylating chitin which a kind of animal polysaccharides, present in the shell of shellfish, such as crabs or lobsters, and is known as the ACE inhibitory substance. Chitosan is a polysaccharide linked by β-1,4-bond of D-glucosamine, and includes α-chitosan derived from shellfishes, β-chitosan from molluscs, and γ-chitosan from microbial strains.
Strictly speaking, chitosan can be defined as a chitin derivative, and acid-soluble chitosan is generally called “chitosan”. Examples of water-soluble chitosan include CM-chitosan (carboxymethyl-chitosan which carboxymethyl group is given by a chemical numerical formula), S-chitosan (oligosaccharide-chitosan), SCM-chitosan (N-sulfide derivative of N-deacetylated CM chitin), HP-chitosan (hydroxyl-propyl-chitosan), etc. Also, according to molecular weight, monosaccharide is called “glucosamine”, a complex of 2˜9 monosaccharides is called “oligochitosan”, and a complex of more than 10 monosaccharides is called “chitosan”.
To make patients with hypertension or diabetes, avoid excessive intake of salt with low purity, such as a mixture of potassium chloride (50%) and sodium chloride (50%), has appeared, but its effect on hypertension has not been proved yet.
Meanwhile, Korean patent publication 95/5196A disclosed a liquid salt seasoning comprising a mixture of salt and chitosan. However, this patent application has no mention of a blood pressure lowering efficacy, and also has problems that it is not easy to mix seasoning liquid with 1˜3% of chitosan, since it is difficult for chitosan generally being participated in alkaline water due to having an isoelectric point of pH 6.5, to be dissolved, and chitosan with a high-molecular weight is in a gel form even in acetic acid due to its high viscosity.
Furthermore, methods for producing chitosan salt are known, in which chitosan dissolved in organic acid is mixed with salt solution, and the mixture is subjected to stirring, evaporating, drying and crystallizing steps (Korean patent publication KR 01/00706A and KR 01/103538A). However, KR 01/103538A has no mention of the blood pressure lowering efficacy of the chitosan salt. KR 01/00706A suggests the blood pressure lowering efficacy of the chitosan salt, but has a problem that it requires the recrystallizing step so that production process is complex and a great increase in production costs is caused upon the mass production of the chitosan salt.